The present invention pertains to a device for feeding preferably liquid or gaseous fuels into a combustion chamber corresponding to the preamble of patent claim 1.
A device of this class for feeding liquid fuel, e.g., oil, into a combustion chamber is disclosed in DE 44 15 863.
An inset, which has a truncated cone-shaped design at its end located adjacent to the discharge orifice of the nozzle body, is arranged here within the nozzle body. The jacket surface of this truncated cone acts as a sealing surface, which cooperates with a truncated cone-shaped hole provided on the nozzle body, and the limiting surface of the said hole likewise acts as a sealing surface.
Flow channels, whose particular cross sections form the entire flow cross section for the fuel, are milled into the truncated cone-shaped jacket surface of the inset for the flow of the fuel. This flow cross section determines the amount of fuel reaching the discharge opening via a swirl chamber arranged in front of the discharge opening of the nozzle body. Since the total flow cross section for the fuel shall be kept relatively small, on the one hand, the velocity of the fuel flowing in shall be substantially increased and, on the other hand, a swirl shall be imposed on the fuel flowing in on its path from the inset to the swirl chamber or to the discharge opening due to the tangential arrangement of the flow channels relative to a base circle, as a result of which extremely fine atomization shall be achieved, which shall guarantee good combustion with high calorific output and a low percentage of pollutants.
Since the inset is held within the nozzle body by a pressure piece, an equal quantity of fuel always flows to the discharge opening regardless of the required output of the burner. This very easily leads to a supersaturation of the fuel mist and consequently to a reduction in the efficiency of the burner as well as to an increase in the percentage of pollutants. Since the feed of fuel cannot be stopped quickly enough when the burner is switched off, a plurality of drain holes leading to a central tank line are provided in the inset for excess fuel to prevent the dripping of the fuel.
Since the amount of fuel being discharged from the discharge opening of the nozzle body cannot be regulated, this device always operates with a continuous flow of an equal amount of fuel regardless of the required burner output. The device must therefore the removed and the inset must be replaced with another inset with a correspondingly adapted total cross section of the flow channels to adapt the amount of fuel to the required burner output. Even though it is described in this connection in DE 44 15 863 that the tank line can be closed by a valve and the amount of fuel flowing back can thus be fed to the burner, so that the burner can allegedly be used with two stages or even with an infinite regulation, this is disadvantageous insofar as it is no longer possible as a result to return excess fuel. On the one hand, the possibility of fuel dripping is substantially increased as a result and, on the other hand, the risk arises, especially when the reserve in the tank has been used up nearly completely, that the flow channels and/or the drain holes become clogged by contaminants present in the fuel or by fuel deposits, as a result of which an unacceptably high pressure may build up in the entire system.
The basic object of the present invention is to provide a device of this class which makes it possible to adapt the amount of fuel to be fed into the combustion chamber to the particular required output of the burner without any change in design. This shall also be possible during the operation of the burner.
This object is accomplished in a device of this class by arranging an actuating element for the sealing element in the cavity of the nozzle body, which said actuating element can be moved by the fuel to be fed in against the force of an end support arranged in the cavity in a first direction to release the discharge opening of the nozzle body and in a second direction opposite the first direction by the end support to close the discharge opening.
Due to the conversion according to the present invention of the pressure with which the fuel is led into the cavity into a force for the actuating element, the actuating element and, as a result, the end support are first moved in a first direction against the resistance of the end support. As a result, the sealing element is moved away from the discharge opening in the nozzle body, so that the fuel reaches the discharge opening of the nozzle body and from there the combustion chamber under the effect of the pressure still prevailing in the cavity. As a result, a pressure drop reducing the force for the actuating element is generated in the cavity despite the continued feed of fuel into the cavity, so that the force originating from the end support now predominates and the actuating member and consequently also the sealing element are returned opposite their first direction of movement into their starting position, in which the sealing element will again close the discharge opening of the nozzle body. Since this process occurs repeatedly as many times as desired, a pulsating fuel flow is generated in the combustion chamber, which can be dimensioned such that the fuel cone in the combustion chamber will not separate if the pressure in the fuel feed line and the force for the actuating element, which is derived herefrom, and the force of the end support are dimensioned correspondingly.
Both the fuel consumption and the amount of pollutants generated can thus be optimized in an especially simple manner. Since the discharge opening of the nozzle body is opened during a relatively short time interval only, during which the actuating force predominates over the force originating from the end support, dripping of the fuel is practically ruled out.
A solution that functions in a simple manner from a design viewpoint and quickly and does not require any transmission device is obtained by the actuating element being formed by a piston, to which the pressure of the fuel to be fed in can be admitted, and which is preferably made in one piece with the sealing element.
To generate the opposing force for the piston, the end support has a compression spring, which is supported against the piston at one end and against an abutment arranged in the nozzle body at the other end.
An advantageous embodiment of the abutment for the compression spring, which makes it possible to change the characteristic of the compression spring and consequently to adapt the force of the end support to different pressure conditions in the fuel feed line in a simple manner, is obtained if the abutment is formed by an adjusting screw, whose relative position in relation to the nozzle body can be set by a movement thread.
Limitation of the maximum size of the flow cross section for the fuel in the area of the discharge opening is made possible if the end support has an adjusting device having a stop (counterpiece) for limiting the path of movement of the piston.
A compact design of the abutment and the adjusting device is obtained if the latter is arranged coaxially to the abutment and has a controllable adjusting member for changing the distance between the piston and the stop (counterpiece).
To achieve the controllable movement of the adjusting member, an adjusting device which can be actuated pneumatically, hydraulically or mechanically may be associated with the adjusting member.
It is favorable in terms of the design to divide the cavity into two chambers, the actuating element and the sealing element closing the discharge opening being arranged within the first chamber, whereas the compression spring of the end support is arranged in the second chamber.
To make it possible to change the force for the actuating element under identical pressure conditions within the fuel feed line, the cross-sectional area of the first chamber can be changed by inserting bushings of different internal diameters.
The holes of the bushings may be designed as stepped holes, the particular area with the large diameter acting as a guide for the piston and the particular area with the smaller diameter compared with that diameter acting as a guide for a cylindrical attachment of the sealing element.
To make it possible to complement the force of the compression spring by an additional fore and thus to achieve an increased flexibility of adaptation of the force of the end support to different pressure conditions in the fuel feed line, the second chamber has an inlet for a feed channel to generate a back pressure to the pressure that can be built up in the first chamber by the fuel fed in.
To guarantee a pressure that does not exceed a presettable maximum pressure within the second chamber, the latter has a connection for a tank line having a pressure-limiting valve.
To achieve the most uniform pressure distribution possible within the second chamber, the inlet for the feed channel and the connection for the tank line are preferably arranged at points of the second chamber that are located diametrically opposite each other.
To achieve the most uniform possible application of the force of the piston, a bushing, which surrounds the compression spring and whose length can be changed telescopically, is arranged within the second chamber between the abutment and the diaphragm. The bushing is advantageously provided with cross holes for the passage of the pressurized medium.
To make it possible to easily replace the sealing surfaces provided on the nozzle body and also to machine or even to retouch them without difficulties, these sealing surfaces are provided on replaceable insets, which are accommodated by a carrying part detachably connected to the nozzle body.
To feed air into the combustion chamber, the nozzle body and the carrying part have essentially the same external diameter, and the nozzle body or the carrying part is detachably connected to an outer part, which is designed as a hollow body and is provided with at least one air feed channel.
If the air feed channel is directed essentially in parallel to the longitudinal axis of the outer part and is open toward the hole of the outer part, it is advantageous for the internal diameter of the outer part to be larger than the external diameter of the nozzle body or of the carrying part, so that the cross section of the air feed channel can be changed by inserting compensating bushings of different external diameters.
Favorable feed of the combustion air as well as good mixing of the combustion air with the fuel can be achieved if the shape of the air feed channel is adapted to the outer contour of the carrying part in the area of its end located adjacent to the carrying part and its free end is expanded in a funnel-shaped manner.
To prevent the pressure within the fuel feed line or within the first chamber from rising above a selectable maximum value, the fuel feed line has, preferably in the immediate area of the nozzle body, a pressure-limiting valve, which connects the fuel feed line to a tank line above a maximum allowable pressure.
To always guarantee a minimum pressure for the actuating element within the first chamber, the fuel feed line has a pressure-regulating valve, which is preferably arranged in the immediate area of the nozzle body and blocks the flow to the first chamber below a settable minimum pressure. As a result, the function of the actuating element according to the present invention is ensured, on the one hand, and, on the other hand, fuel is prevented from dripping into the combustion chamber through the discharge opening when the pressure within the first chamber is too low.
It is advantageous for at least part of the wall of the cavity and an area of the piston to consist of magnets or antimagnetic metals, which support or initiate the pulsating opening and closing of the discharge opening by current pulses.
To additionally set the piston into rotary motion during its working movement, the piston has means to derive a rotary movement from the pressure energy of the fuel.
To make it possible to meter even very small quantities of fuel reliably and accurately, the sealing surface of the sealing element is divided into a plurality of sealing surface sections, which are arranged in a stepped manner and cooperate with sealing surface sections of the sealing surface of the inset, which are arranged in a correspondingly stepped manner.
To achieve an especially intense mixing of the fuel with the air to be fed in, at least some of the discharge slots of the air feed channel are arranged and directed such that the air flow discharged from the air feed channel meets the fuel mist being discharged from the discharge opening in the area of the discharge opening.